JPH01503082A - Increased low energy high purity oxygen release pressure - Google Patents

Abstract

The low energy triple distillation pressure process for producing high purity industrial oxygen is improved in several ways, including higher O2 pressure, higher recovery of both oxygen and crude argon, and lower N2 content in the argon. This is done with the traditional triple pressure column arrangement (columns 22, 24, and 27 of FIG. 1) preferably by totally condensing liquid air in reboiler 21 and then splitting it with valves 42 and 43; by providing all LN2 reflux duty from reboiler 26; by evaporating product oxygen in 23 with partially condensing air; and by intermediate refluxing column 27 with condenser 28 which provides a separate vapor stream to column 22.

Description

[Detailed description of the invention] The present invention provides a method for producing large amounts of highly pure (at least about 8% pure) oxygen by fractional distillation of air. and optional symbiotic oxide argon with high recovery levels and low energy requirements. and a method and apparatus for achieving the same.

The present invention achieves the above objectives while achieving a high 0. Reduced discharge pressure and major costs are possible. Ru.

Victory! ! This application is filed under U.S. Pat. No. 4,578,095 (No. 19 Patent dated March 25, 1986, PCT application 1!585101596 related thereto This is a partially pending application published on February 27, 1986 (1086101283). Ru.

The conventional double-pressure air distillation method for producing high-purity oxygen uses an HP rectification column and top steam. The effluent from the nitrogen removal tower (LP tower) is reboiled by latent heat exchange. less In most cases, approximately 60% of the supply air, sometimes as much as 90%, is supplied to the HP rectification column. In this way, sufficient LNt is secured for both towers and for achieving a large amount of oxygen recovery. . The traditional method is described in the technical literature, ``High Oxygen Generation by an Improved Two-Bath Process.'' ” (M. Straitsk and J. Dobo). Lucitary (M, 5treich and Dvorschak), 14th edition International combination of rare onal Congress of Refrigeration) Paper A3 ．． 18, September 1975, Moscow, Sponsored by The Internacional Institute The International I n5 orientation or Refrigeration)). LP column is al nitrogen stripping section, nitrogen stripping section and This side arm consists of a Rougon rectification side arm, which has two stripper The main column is connected to the main tower at the junction of the connecting sections.

Several attempts have been made to reduce the energy required to produce distilled high-purity oxygen. It is. Common features in successful attempts are: l) rectification of argon, N, removal; 2) the N removal column is operated at a lower pressure than the removal column; The rectifier N, is reboiled by latent heat exchange with the partial condensed air instead of the air 3) argon stripping the N, removal column and the argon distillation column at the bottom of the ribs, i.e. Feed the argon column with N, its side stream rather than the bottom product of the removal column. That's what I'm doing.

Despite these significant and substantial improvements in high-purity oxygen production, the There are still some problems as mentioned above.

U.S. Pat. No. 3,688,513 to Streich et al. incorporates the above three features. A heavy pressure, high purity 08, air distillation apparatus and method is disclosed, which further comprises: characterized.

a) Reboiling the N* removal column by partial condensation of the air fed to the HP rectification column , b) No recovery of liquid argon, i.e. no recovery of crude argon by means of a pump. c) latent heat exchange using HP rectification column top N; By reboiling both the argon column effluent and the middle height of the N removal column. , d) Evaporate the product oxygen by latent heat exchange with the HP distillation column top N. that, and e) Process refrigeration is by conventional methods (air or N, expansion).

This disclosure indicates that no argon was recovered. Production pressure is undesirably low There are some problems. In regions where argon is valued, its value is solely energy consumption decreases 1; approximately equal to value, and therefore reduces any overall benefit. The points will also be cancelled. In the absence of a market for crude argon, due to the low argon production pressure ,0. A substantial addition of a product compressor to the main equipment is required. Also, the above As shown in Figure 2 of the Straitsk and Dvorschak literature, the 02 recovery The rate is lower than traditional methods (94% vs. 98%). This is also the main cost increase

Tomisaka's U.S. Patent No. 4,507,134 incorporates the three features mentioned above. Purity, air distillation equipment and method are disclosed, which are further characterized in: Ru.

a) approximately half of the feed air is fed directly to the HP rectifier; b) most of the remaining Feeding a two-step continuous process, i.e. i) reboiling the N removal column by partial condensation and then 11) reducing the remaining N by total condensation. ．． C) vaporizing the product, C) transferring the oxygen-enriched liquid air of step b) to a HP rectification column; Then, the oxygen-deficient liquid air from step b) is transferred to 1i) the Nl removal column as intermediate residue, respectively. to supply d) recovering crude argon from the top of the argon column by means of a vacuum compressor; e) Similar to Straitsk et al., the HP rectifier, N, and LN for residual removal column are Obtained by two latent heat exchangers (one is an intermediate reboiler for the N, removal column) thing, f) conventional air expansion refrigeration; g) Pressurize and evaporate liquid oxygen using an atmospheric leg.

This disclosure states that at least a small amount of crude argon is not recovered. Discharge pressure is HP rectification N, the benefit is greater than that possible with latent heat exchange than Straitsk et al. There is a point. However, this has the following disadvantages. 1) Total amount of supplied air Slightly less than half of the air is subjected to partial condensation, so a high air supply pressure is required. be. 2) LOX is evaporated by completely condensing oxygen-deficient air instead of partially condensing it. Therefore, 0. The increase in discharge pressure is very small. 3) High 02 recovery rate and high Al It is not possible to achieve both flow and insufficient mid-section reboiling). 4) By normal refrigeration, HP rectifier and alkaline Diverts an undesirably high percentage of supply air around both sides of the gas stripper I'm letting you do it. 5) The latent heat exchanger from the top of the HP to the N, removal tower/mid height is also connected to both sides. Reboils are diverted around the argon stripper on the side to better achieve high purity oxygen. make it difficult to Also, it is N, the bottom section of the stripping section. Reduces reboiling in crude argon, making it very difficult to achieve lower levels of N in crude argon. Let it be. This problem has also been experienced by Streich et al.

U.S. Pat. No. 4,578,095 discloses high purity oxygen and the desired discloses a triple pressure air evaporation device and method for symbiotic argon production by is further characterized by the following points:

a) Means for crude argon recovery (either as vapor or liquid, or both) , b) Cooperative means for providing mid-height vapor to the N, removal column (the supply or reboiling argon distillation column).

This equipment allows for a significant increase in the reboiling rate above the bottom of the argon distillation column. It is important to obtain high yields of both &argon.

Additional optional features of this '095 patent disclosure include: It will be done.

l) Similar to Streich et al., the effluent of the N removal column was added to the feed air to the HP rectification column. 2) normal boiling by either N, or air expansion. refrigeration, 3) evaporation of LOX in HP rectifier N, and 4) HP rectifier top and N, the elimination of another latent heat exchanger between the middle height of the removal column, i.e. HP rectification The latent heat exchanger between the top of the column and the bottom of the argon column is designed with full LN capacity. By doing so, you will gain the following benefits: i) N, due to increased reboiling through the critical lower section of the stripper; N, the stripping section is in coarse argon, the level is less N, reducing to a lower level by a stripping stage; ii) Increased redistillation of the argon stripper to reduce the need for fewer trays. 0. purity is now easier to achieve; 1ii) one less heat exchanger reduces the overall Substantial reduction in required costs.

This latter inventive feature 4) is one important aspect of this continuation application.

The °095 patent provides substantially increased recovery levels of crude argon and high purity oxygen. Although reduced N, levels in crude argon are possible, it is due to two deficiencies: Hold the points. 1) Os biointimidation is undesirably low, reducing major costs to 0. 2) The top of the argon column is frozen with argon. to come undesirably close to. In addition, the intermediate part of the argon tower was If it is to be kept at a desirably high 0. Not the content.

Low energy, high purity 0. Desirable improvements to double pressure distillation include high O2 Yield, high 0. discharge pressure, high recovery and purity of crude argon, low supply air pressure, Large limits to Rougon freezing, and minimal increase in major costs or preferred includes practical reductions.

The combinations of features necessary to achieve these objectives are individually known to some extent in the prior art. However, nothing is known about the low-energy triple pressure method for producing high-purity oxygen. and the specific combinations disclosed herein necessary to achieve the desired improvement are Not very well known.

Re-boiling the bottom of the nitrogen removal column (brate) by total condensation of a small portion of the feed air This is known [US Patent No. 3210951.4208199.44103] 43 and 444859].

Feed liquid air is routed to two intermediate reflux streams (one for the HP rectifier and the other for the N, It is also known to divide the 10343 and 4448595]. U.S. Patent No. 3,798,917 describes liquid air Disclose the three-way division of.

In addition, the oxygen products are vaporized by latent heat exchange with the air that is supplied to the HP rectifier and is fractionated. It is also known to emit light [US Pat. No. 3,113,854.3371496.3] 327489 and 4560398].

In many process diagrams, for example, an LP column is replaced with N in an HP rectification column.

When reboiling is done by air condensation, LOXBOIL The pressure is slightly higher than the LP tower bottom pressure. This pressure increase can be achieved with liquid oxygen pumps. However, the preferred method is to use the atmospheric leg or hydrostatic head of a liquid oxygen column. boiling the LOX at an appropriately lower altitude than the LP bottom reevaporator. It is to make it possible. This is US Patent No. 4133662.4507134 and 45 60398 and South African Application No. 845542 (dated 18 July 1984) (Izumichi, Izumichi, and Ohyama).

The work produced by the refrigeration expander is used to compress a portion of the compressed supply air for additional heating purposes. It is also known to apply The increased compression obtained is very economical. Ru. This is because the driving force is free, and the main cost of the compander is Is there almost no difference in the main cost of an expander with other means of absorbing biopower? It is et al.

The additionally compressed air is then subjected to conventional refrigeration (German patent application no. 285 450) No. 8, Issue 06/19/go, filed by ■-de) or TCLOXBOIL ( US Patent No. 4133662, Soviet Patent No. 756150 and South Africa Application No. 845542 (cited above)).

When applying liquid air/intermediate residue to an LP distillation column, the air supplied to the HP rectification column The initial amount of body air added is reduced by a substantial 1:1 for a given recovery and purity. It is possible. The advantage of retaining in the middle part is that as the amount added increases, the “pinch” is reached. continues to increase, and the operating line approaches its equilibrium line closely. Furthermore, the point Adding intermediate retention beyond the point reduces that advantage. i.e. the required peak The amount of air that must be fed to the HP rectifier to obtain partial reflux cannot be further reduced. stomach. The same advantages are obtained from an intermediate reflux HP rectifier.

Regarding the air separation method that uses liquid air for intermediate reflux, the optimal amount of liquid air remaining is L. Approximately 5-10% of feed air for both P column and HP rectifier. faster A lower liquid air flow rate will result in no additional reduction in the amount required for top (LN2) reflux. I don't do it.

Some prior art disclosures provide air to the cooling box at two different pressures. It is necessary to One example is the group of compander-processed refrigeration patents mentioned above. With Additional examples include the use of high pressure air to evaporate liquid oxygen (U.S. Pat. No. 37,540). 6.4133662 and 4372764), high pressure air is supplied to the second high pressure rectifier. (U.S. Pat. Nos. 4,356,013 and 4,604,116) and high pressure Nitrogen generation method in which a low pressure column is reboiled by total condensation of fruccine (U.S. Pat. No. 444) No. 8595) is included.

Conventional cryogenic air separation/process flow diagrams are based on total separation using one of two conventional methods. Obtaining large amounts of refrigeration for the process. In other words, one of the HP rectification column top nitrogen part is work-expanded to the discharge pressure (slightly lower than the top pressure of the LP column) or Either expands a portion of the feed air to the LP column mid-height pressure. US Patent No. 3324788 describes the above two methods in the above process flow diagram. However, for economic reasons, only one or the other is usually used.

Refrigeration comes at the expense of heat leakage, heat exchanger inefficiency, and other effects. most modern Even with efficient expanders in the separation plant, obtaining the necessary refrigeration requires An inflator flow of about 8-15% of the inlet airflow is still required depending on size and design.

A large flow of refrigerated gas is inefficient in achieving the above objectives for the following reasons. liquid flow The argon stripper bypasses the 0. It may become difficult to improve purity. and. Since it is not utilized in the argon rectification column, the recovery rate of argon may decrease. and. Since the residual LN is not used for generation, the 0° recovery rate decreases. .

Although not essential to the present invention, it solves at least some of the problems associated with conventional refrigeration. A description of each of the three refrigeration techniques avoided is included in the present disclosure. The first is as mentioned above. The amount of frozen sea urchin can be reduced by subjecting the frozen sea urchin stream to heating and compandering treatment. That is. The second is to partially expand the HP rectifier feed air. this requires a slightly higher air supply pressure (approximately 5 to 12 psi higher), but oxygen and and argon recovery are substantially increased. The third is liquid nitrogen at intermediate pressure. is preferably evaporated by latent heat exchange with the liquid at the middle height of the argon column, and is then discharged. It is to expand the work to the output pressure. U.S. Patent Nos. 2,812,645, 390,520 No. 1 and No. 4,303,428 describe a variation of the second technique.

Other prior art disclosures suitable for the present invention include U.S. Pat. and No. 4605427.

Disclosure of invention In order to achieve the above objectives and avoid the above problems, conventional low energy We have found that three additional features should be incorporated into a process diagram. Ta. First, the intermediate part remains in the argon tower and the accompanying N, and the re-retention in the removal tower. A combination of mid-range increase in boiling is disclosed in US Pat. No. 4,605,427.

The second is LN with a single latent heat exchanger that reboils the bottom of the argon column, Achieving residual capacity, which enables HP top-N, removal tower/mid-height latent heat exchanger The goal is to eliminate The third one is newly disclosed in this specification. of the total supply air in a predetermined amount that is no more than about 25%, preferably no more than about 20%. The resulting liquid air stream is reboiled by condensation, one for the HP rectification column and one for the HP rectification column. is split into two intermediate reflux streams for the N, removal column.

Only when all three of the disclosure improvement methods described above are incorporated will the following improvements be achieved. It becomes possible. Relatively high pressure (approximately 1,6 A TA) NOLOXBOIL: Complete 07 recovery and 0. Purity: about 1% or less N, content High recovery of argon with approximately 95% purity; sufficient temperature limits for argon freezing (on the order of 3); only 5 separate latent heat exchangers and 1 expander (or pumper): and no need for liquid pumps or difficult tower relative height arrangements .

However, it should be emphasized that each of the above three features alone can reduce energy consumption for high-purity oxygen. Contribution to better improvement than disclosure of prior art regarding Lugie triple pressure process diagram It is possible. In the various environments encountered when implementing air separation technology, the above-mentioned advantages are Not all characteristics necessarily indicate value. For example, without recovering crude argon. If discharging to The method does not offer value over alternatives that could additionally reduce energy consumption. death Therefore, each of the three characteristics described above can be used not only when combined with the other two, but also when combined with the other two. It has value in other environments as well.

More formally, in one aspect the invention separates purified and compressed supply air. The oxygen product of at least 98% purity and the desired component of crude argon are produced by distillation. In producing the product, a) latent heat exchange with the main part of the feed air to be partialled; evaporates the oxygen products by b) The uncondensed residue of the main portion is rectified in a high pressure (HP) rectification column to form a top part N and a bottom part. produces particulate liquid, C) A small portion of the feed air is completely condensed in the reboiler of the nitrogen removal column to the bottom of the column. d) splitting the liquid air into two streams, each containing the Hp Supply the distillation column, the N, and the removal column for each intermediate section retention, e) liquid phase boiler liquid. f) substantially nitrogen-free sidestream liquid oxygen; The argon mixture is collected below the feed height and at the middle height of the removal column, g ) The liquid side stream of the argon distillation column is distilled to produce crude argon and overhead product. h) converting the liquid oxygen bottom product into a nitrogen removal column; Argon is recovered from both distillation columns, i) increasing the pressure of the liquid oxygen to the evaporation pressure of step a); and j) increasing the pressure of the pressurized liquid oxygen to the k) recovering said crude argon and said vaporized oxygen; It consists of the method of using it as a sign.

In conjunction with the above, or separately and independently, the present invention provides Fractional distillation of air produces an oxygen product of at least 98% purity and optional components. In producing the crude argon co-product, a) 0.0. High pressure (HP) ) is rectified in a rectifier to produce N, a top product and a bottom bottom product; b) Supplying the liquid phase of the kettle to a nitrogen removal column and distilling it to produce the kettle removes nitrogen from C) latent heat exchange of the bottom of the nitrogen removal column with at least a portion of the feed air to be partialized; Boil it again by replacing it with d) supplying said substantially nitrogen-free sidestream liquid oxygen-argon mixture; collected from the middle height of the nitrogen removal column lower than the height of the nitrogen removal column; e) Distilling the liquid side stream of the argon distillation column to produce crude argon and overhead raw material. f) HP rectification column top N, and argon column reboiling at least the bottom of the argon column by exchanging latent heat between the effluent; Additionally, both the HP rectification column and the N removal column have substantially all of the LN retained at the top. Well then g) Evaporating the liquid oxygen/bottoms product of both the argon column and the nitrogen removal column; The method is characterized in that the product is recovered as a product.

Further additional inventive features reside in the appended claims and as detailed below. Describe it on the drawing.

Brief description of the drawing 39 drawings simplify low energy triple pressure air distillation process for high purity oxygen production It is a schematic process flow diagram. Figure 1 incorporates all three features. Sunawa Total condensation-reboiling by liquid air division, complete reflux capacity of a single heat exchanger power, and reflux in the middle of the argon column. These features are due to compander processing - Enables high pat/partial condensation LOXBOIL evaporator along with air refrigeration. Also, The desired amount of 0.0% obtained from the gama liquid but different from the liquid liquid. Aluminum liquid with content level 1 illustrates a novel means for feeding each reflux condenser for a gas column;

The latter includes a countercurrent gas-liquid contact area of the boiler liquid and two continuous condensers instead of parallel ones. Supply is included.

Figure 2 shows a situation where high argon recovery is not worth the additional energy savings. shows. The necessary energy is added by subjecting the totally condensed and reboiled air to a compander treatment. Even if the argon recovery is lowered to An alternative refrigeration technique is shown below. Furthermore, Figure 3 shows that there is no interest in energy reduction ( (e.g. low energy prices) represents a third environment where there is more interest in increasing recovery rates. vinegar. By using refrigeration by partial expansion of rectifier air, maximum LN, It can be used to increase elementary recovery.

Most preferred mode of carrying out the present invention In FIG. 1, compressed and purified supply air is cooled to approximately the dew point in the main heat exchanger 20, The small portion of 25% or less is N! It is sent to the reboiler 21 of the removal column 22 where it is It is completely deflated and the main part is sent to the PCLOXBOIL evaporator 23 where it is treated with acid. Condensation occurs while boiling the elementary products. The uncondensed part of the air is removed by a phase separator 25. After optional phase separation, it is fed to the HP rectification column 25 and rectified to form the top N and liquid oxygen-enriched air. Produces a bottom product (commonly called scum). The top steam Nt is A single latent heat exchanger in distillation column 27 feeds only reboiler 26. Obtained from 26 liquid N, is divided between the rectification column 24 and the top of the column 22, the latter having an explicit exchanger 39, a pressure Via a force drop valve 40 and a phase separator 41. As shown in the diagram, add the liquid Combined with the partial condensation liquid of 3 or alternatively held separately (slightly different composition) can be fed in liquid phase to the column 22, but first at least a portion is The argon column 27 is left behind by evaporation.

The intermediate residual condenser 28 and the top residual condenser 29 of the argon column 27 are each capable of It is important to supply a vapor stream with as high an Ot content as possible to each height of the N removal column 22. Ru. 0.28 in steam. The higher the content, the more it can be introduced into the column 22. height decreases. Therefore, the minimum reboil requirement of column 22 below such height is The amount decreases and the reboiler capacity of the column 27, which is lower than the condenser 28, increases accordingly. do. This increased reboiling results in increased argon recovery. Similar considerations apply to condensers Added to 29.

Typical condenser LMTD at about 1.5 and argon column top at about 0.97 ATA To enable pressure, the vapor sent from condenser 29 to column 22 via valve 30 is , at least about 35% of 0. It should have a content. This is a part of the liquid. This can be easily done by shrinking. However, the same height 0. The content of liquid is No supply is available to the condenser 28 via the valve 31. Toad A countercurrent gas-liquid contact area 32 is provided to utilize such liquid obtained from the liquid. decrease Pressurized head fluid is supplied above area 32 via a pressure drop valve 34. Contactor 32 The amount of steam produced by the condenser 29 entering the condenser 29 is determined by a control valve 30. Top of contactor 32 The steam released from the section is supplied to the column 22 via a check valve 35. any bar Bulbs 45 and 37 optimize the amount and composition of the liquid supplied to the condenser 28. It can be changed. Similarly, the bypass valve 38 connects the condenser 29 via the contactor 32. It is possible to control the amount of bath fluid supplied, especially to achieve the desired Useful for maintaining limits.

The overall result is that the gama liquid can be in a liquid phase, a gas phase or a combination (hereinafter referred to as a fluid phase), respectively. is fed to the column 22 at different heights as three different streams, which can be called

It is evaporated in one or both of the condensers 27 and 28 instead of the boiling liquid. It is understood that the liquid can be at the intermediate height of the column 22 at each suitable height. . This indicates that there is no real difference in the thermodynamic or energy efficiency of the process diagram. Although it does not have any effect, does it impose some kind of restriction on the relative height arrangement of the towers? or liquid pumping is required.

The condensed liquid air of 21 is passed through the HP rectifier 24 by the cooperative action of valves 42 and 43, respectively. and two intermediate reflux streams for column 22. Each flow is the total supply air It should be no more than about 15% of the volume, otherwise you lose the same benefits of splitting.

Liquid oxygen-argon gas containing 95% oxygen and less than about 0.1% Nt The waste stream is recovered from column 22 and fed to column 27 via transport means 33. , this can be a pump, a check valve or simply an atmospheric leg (relative (depending on tower height). Liquid oxygen/bottoms product (brate) of both columns 27 and 22 is transported to the LOXBOIL evaporator 23 by transport means 44 and 36. 23 is 2 7 or 22, so in the case of 36 and 44 it is simply a valve. , but it places the necessary pressure increase at a lower altitude where the atmospheric leg generates it. It is preferable to place Similarly, crude argon can be recycled as either vapor or liquid. The atmospheric leg can be used to evaporate it at increased pressure.

The process refrigeration technique illustrated in FIG. 1 uses N in the small portion of the supply air.

Although conventional expansion to removal column pressure (47), the purpose of warming the expanded air is Compression is applied with a compressor 46 powered by the expander. This compan The processing reduces the flow required by the expander to about 374% of what would otherwise be required. That is, it is typically reduced to 10% or less of the total amount of supplied air. Of course, further Large flow reductions are possible with additional externally powered compressors. Both decreases It increases the air available to the HP rectifier and then produces more LN. This is desirable because it results in increased O1 recovery. For applications under examination As described, conventional or compander-treated air refrigeration can be replaced by Replacement of conventional or compander-treated N-year-old refrigeration is possible. Further additional refrigeration A selection is possible with two embodiments shown in FIGS. 2 and 3. Also, Compan The compression power can be applied to other beneficial purposes as illustrated in FIGS. 2 and 3. I can do it.

FIG. 2 shows a similar basic three-column configuration. However, different steam inflating (intermediate pressure Nt), heating and compressing different streams (total condensation and reboiling stream), and This shows a slightly different arrangement of the argon tower remains. Three important features still exist. sand Namely, total condensation and reboiling of the N removal column by liquid air division into two intermediate retentates. , at least two vertically spaced argon towers (each with a N removal tower) (having steam that combines streams of different compositions at different heights), and a single heat exchanger The total amount LN achieved by the vessel is the residual capacity. The combination of such features makes efficient Supports PCLOXB01L evaporator. Components 220 to 245 are the corresponding numbers. The components are the same as those in Figure 1. However, corresponding to 25.30.32 and 35 The components are not shown because they are not necessary. A contactor is not required in this process diagram. Why Columns 227 and 224 are approximately smaller than columns 27 and 24 due to the compander treatment. Since the condenser 229 is operated at a low temperature of 1.5 to 2, no extra contactor is used. High 0. Content liquid can be generated for valve 231 and condenser 228 It is from. Of course, in certain situations it may be desirable without excluding it. can.

The key difference from FIG. 1 is the LINBOIL condenser 248, which is the valve 2 partially depressurized LN is supplied via argon column 227 . The argon stream in HP rectification column 224 or column 227 is Generates an expanding vapor flow that is not diverted to any of the pipping sections. N, The steam is partially warmed at 220 and then work expanded in an expander 250. of expansion Because the pressure ratio is lower, a higher flow rate is required, on the order of 15% of the supply air. . 248 substantially reduces the available reboil in the top cefsilane of 227. Therefore, recovery of crude argon is also reduced. However, the increase in LNt causes compression This means that the container 251 can be applied to the air supplied to 221, so the complete O 2. Supply pressure can be reduced while maintaining recovery.

FIG. 3 illustrates another advantageous combination of the disclosed features. Ingredients 320-345 are This is the same description as the corresponding component in the 200s in FIG. Ingredient 352 generally includes indicates the compression and purification effect of the supplied air. In FIG. 3, the vapor expanded by an expander 353 The gas stream is the main part on its way to evaporator 323 and then to rectification column 324 . Since it expands at least 75% of the air, it has a very small expansion pressure ratio. only is necessary.

Compressor 354 is conveniently used to provide approximately 1/4 of the compression consumed by 353. used. The net result is that the supply air of 352 is smaller than the supply air of e.g. The pressure must be approximately 0.7 ATA high. Increase in supply pressure (approximately 5-5 , 5 ATA), there is no need to additionally compress the supply to 321; 354 compressions can be applied to the expander feed stream.

This number allows for higher energy input without reducing crude argon recovery. The extremely high 02 recovery characteristics shown in FIG. 2 can be achieved.

The specific combination of advantageous features disclosed and Although specific examples have been given, many others will be apparent to those skilled in the art. Conventional second An HP rectifier/top condenser can be added to either process diagram. re-decompression Boiling can be replaced by total contraction.

The liquid from the harvest can also be collected. Various column and heat exchanger physical forms are also known. , is possible. A low pressure drop tower packing is also preferred, but not required. The expansion capacity is between two or more expanders, including variants consisting of expansion of entirely separate vapor streams. It can be divided into

The intended scope of the invention is not limited only by the claims.

FIG. 1 international search report

Claims (11)

[Claims] 1. Acid of at least 98% purity by fractional distillation of purified and compressed feed air In producing the elementary product and the optional crude argon co-product, a) evaporating the oxygen products by latent heat exchange with the main portion of the feed air being depleted; , b) The uncondensed residue of the main portion is rectified in a high pressure (HP) rectification column to form top N2 and bottom N2. produces particulate liquid, c) A small portion of the feed air is completely condensed in the reboiler of the nitrogen removal column to produce a effluent from the column. Re-boil the d) splitting the liquid air into two streams, each to the HP rectification column and the N2 removal column; e) at least one fluid-form boiler liquid for each intermediate reflux; f) substantially nitrogen-free sidestream liquid oxygen-alcohol; g) collecting a nitrogen mixture from a mid-level of the N2 removal column below the feed height; The liquid side stream of the argon distillation column is distilled to produce a crude argon overhead product. and h) transferring the liquid oxygen bottom product to a N2 removal column and an alkaline Collected from both of the Gon distillation towers, i) increasing the pressure of the liquid oxygen to the evaporation pressure of step a); and j) increasing the pressure of the pressurized liquid oxygen to the k) recovering said crude argon and said vaporized oxygen; A method characterized by becoming. 2. Furthermore, due to latent heat exchange from the top N2 of the HP rectification column to the bottom liquid of the argon column, The effluent from the argon column is re-boiled and all of the N2 is transferred to the HP rectification column for N2 removal. 2. A process according to claim 1, comprising refluxing in both stripping columns. 3. moreover, (a) Steam at the middle height of the argon column and i) Step 1. a) Oxygen-rich liquid ii) Stainless steel, and iii) N2 removal tower/middle height liquid above the feed height by latent heat exchange between the vapors obtained from at least one of the The argon column is refluxed in the middle, and the N2 removal column is placed above the side stream recovery height. and then (b) remove N2 from the vapor obtained by the latent heat exchange. Supply to the middle height of the removal tower 3. A method according to claim 2, comprising: 4. moreover, (a) Steam at the middle height of the argon column and 1) Process 1. a) Oxygen-rich liquid ii) Stainless steel and iii) N2 removal tower/middle height liquid above the feed height by latent heat exchange between the liquid obtained from at least one of the The argon column is refluxed in the middle, and the N2 removal column is placed above the side stream recovery height. and then (b) remove N2 from the vapor obtained by the latent heat exchange. Supply to the middle height of the removal tower 3. A method according to claim 2, comprising: 5. Furthermore, by limiting the small amount of air to 25% or less of the total amount of air supplied, Claim No. 1, each comprising limiting the air flow to no more than 15% of the total air supply. The method described in Section 4. 6. moreover, a) while warming a second small stream of said supply air comprising no more than about 10% of the total supply air; additionally compressed, b) partially cooling the additionally compressed stream; c) partially cooling the additionally compressed stream; Work expansion is carried out, and this is supplied to the N2 removal tower, and then d) powering at least a portion of the compression process by the expansion process; 4. A method according to claim 3, comprising: 7. moreover, a) At least one of the flask liquid and the fractionated liquid is transferred to the top of the argon column through indirect latent heat exchange. supply to the reflux; b) Step 7. having a higher O2 content than either the sluice or the fractionated liquid. a) of A claim comprising supplying an unevaporated liquid as the "derived liquid" in step 3. The method described in box 3. 8. Furthermore, step 1. c) additionally compressing the fully contracted air portion while warm; powering at least some of the additional compression by work expansion of the cooling process evaporative stream; 2. A method according to claim 1, which comprises obtaining the necessary refrigeration. 9. Additionally, the HP rectifier feed air stream is selected for at least a portion of the work expansion. The method according to claim 8, comprising: 10. Furthermore, the latent heat is exchanged with the argon column and intermediate height steam, and the intermediate pressure N2 is increased. Evaporating liquid nitrogen at intermediate pressure by using it as the work-expanding vapor. 9. The method according to claim 8, comprising: 11. Fractionation equipment for producing high purity oxygen from compressed, purified and cooled supply air And, a) High pressure rectification column b) Argon evaporation tower c) HP for latent heat exchange between the vapor at the top of the rectification column and the liquid at the bottom of the argon column; Reflux condenser for rectification column d) a nitrogen removal column refluxed by a portion of the liquid nitrogen from the reflux condenser; e) a N2 removal reboiler for condensing a small portion of the supply air to liquid air; f) Transfer the liquid side stream of the N2 removal column below the feed height to the argon column. tubes for transport to the supply location g) liquid oxygen evaporator h) for feeding the liquid bottom products of the argon column and the N2 removal column to the evaporator; tube i) tubes for supplying the main part of the feed air to the LOX evaporator; j) the LOX evaporator; a pipe for transporting at least the unevaporated portion of air discharged from the HP rectifier; and k) Two streams fed to each intermediate reflux height of the N2 removal column and HP rectification column. Apparatus characterized in that it comprises means for dividing said liquid vitality into two.